Resilient mount for MacPherson strut

ABSTRACT

A resilient mount attaches the upper end of a MacPherson strut to vehicle body support structure. The mount comprises an annular mounting plate, an elastomeric ring, a central sleeve with an attached end plate, and a ball thrust bearing. The annular mounting plate, the central sleeve and the upper bearing ring of the thrust bearing are bonded to the elastomeric ring to form a subassembly. The mounting plate has a central cup-shaped portion which is embedded in the elastomeric ring and trapped between an enlarged head of the central sleeve and the end plate attached to it. The elastomeric ring has integral flexible lips at its lower end which retain the bearing elements and lower race ring and seal the ends of the thrust bearing.

This invention relates generally to a resilient mount for the upper endof a MacPherson suspension strut and more particularly to a resilientmount of the type having an elastomeric ring which cushions the loads ofthe shock absorber as well as the loads of a coil spring which surroundsthe shock absorber.

U.S. Patent Application Ser. No. 928,508 filed by Richard A. Muzechukand Marvin J. Hyma July 27, 1978 and assigned to the assignee of thisinvention shows a resilient mount for the upper end of a MacPhersonsuspension strut which has an elastomeric ring which cushions the loadsof both the shock absorber and the wheel suspension coil springsurrounding it during suspension jounce and rebound.

More specifically, the Muzechuk and Hyma patent application discloses aresilient mount 56 comprising an elastomeric ring 58, a flanged metalbushing 64, a ball thrust bearing 66, 70, 72 formed as a unit handledsubassembly, and a pair of retainer members 74 and 76. The metal bushing64 is bonded to the elastomeric ring 58 and attached to the end of theshock absorber piston rod 36. The ball thrust bearing abuts the lowerend of the elastomeric ring 58 and is retained by trapping the outeredge of the upper race ring 66. The lower race ring 72 rotatablysupports an upper spring support 44 for the coil spring 40. Theelastomeric ring 54 is compressed axially and radially by partiallyenveloping, stamped metal retainers 74 and 76 which are secured togetherat their peripheries. The retainers 74 and 76 help retain the ballthrust bearing and secure the resilient mount 56 to the vehicle bodystructure 12. The preloaded outer portion of the elastomeric ring 54 issubjected to compression forces by the coil spring 40 during suspensionjounce and rebound, while the preloaded center portion of theelastomeric ring 58 is subjected to shearing forces by the piston rod36. The elastomeric ring 58 thus provides different predeterminedstiffness characteristics for the coil spring 40 and the shock absorber32.

Broadly the object of this invention is to improve upon the resilientmount disclosed in the aforesaid patent application by providing asimplified unit which reduces the number and complexity of the parts andsaves weight.

Another object of the invention is to provide a resilient mount in whicha mounting plate and upper race ring mold bonded to an elastomeric ringform a subassembly which improves bearing alignment and contactinterface with the elastomeric ring and eliminates the need for a twopiece retainer.

Yet another object of the invention is to provide a resilient mounthaving a subassembly as noted above in which the elastomeric ring hasintegral flexible retaining and sealing lips which reduces thecomplexity of the thrust bearing and the manner in which it is retained.

A feature of the invention is that the mounting plate is shaped tofacilitate providing independent predetermined stiffness characteristicsfor the shock absorber and coil spring.

Another feature of the invention is that the mounting plate and thesleeve for attaching the piston rod are cooperatively shaped so that theelastomeric .[.suppot.]. .Iadd.support .Iaddend.for the piston rod isrelatively stiff in the lateral direction.

Still another feature of the invention is that the sleeve which attachesthe shock absorber piston rod to the elastomeric ring is designed toprovide a fail-safe device in conjunction with the mounting plate.

These and other objects and advantages of the invention will be apparentwhen reference is made to the following description and accompanyingdrawing, wherein:

FIG. 1 is a partially sectioned front view of a vehicular frontsuspension system employing a MacPherson strut attached to the vehiclebody by a resilient mount embodying the invention.

FIG. 2 is an enlarged cross sectional view of a portion of FIG. 1showing the resilient mount and adjacent suspension structure in greaterdetail.

FIG. 3 is a cross sectional view of a subassembly of the resilient mountshown in FIGS. 1 and 2.

FIG. 4 is a bottom view of the subassembly shown in FIG. 3.

FIG. 5 is a cross section view showing a modified resilient mountembodying the invention.

Referring now to the drawings in greater detail, FIG. 1 illustrates afront suspension system 10 mounted at its upper end on a tower-likestructure 12 of the vehicle body usually associated with the wheel well.The suspension system supports a wheel hub 14 which is rotatably mountedon a spindle portion of a steering knuckle 16. A conventional wheel 18and tire 20 are mounted on the hub 14.

The suspension system 10 includes a lower control arm 22, which may beof the wishbone type, having its inner ends 24 pivotally mounted to thevehicle frame or underbody 26 and is outer end connected by a ball joint28 to the steering knuckle 16.

The suspension system 10 employs a MacPherson strut comprising a shockabsorber 30 which has an outer casing 32 mounted at its lower end in abracket 34, which may be formed on or secured to the steering knuckle16. The shock absorber 30 has an internal piston (not shown) attached toa piston rod 36 which extends out of the upper end of the casing 32 andis flexibly connected to the vehicle body structure 12 by a resilientmount 38 which is the subject matter of this invention.

The axis of the shock absorber 30 does not coincide with the steeringaxis for the wheel 18 which is determined by the centers of theresilient mount 38 and the ball joint 28 and it may or may not intersectthe axis of the wheel 18 depending on the particular application. Forinstance, the mounting bracket 34 may be located above, or in front of,or to the rear of the axis of the wheel 14 an amount sufficient toaccommodate a drive axle in a front wheel drive vehicle.

The MacPherson strut further comprises a coil spring 40 surrounding theupper part of the casing 32 and the piston rod 36. The lower end of thecoil spring 40 is mounted on a lower spring plate 42 secured to theouter casing 32 while the upper end reacts against an upper spring plate44 which is supported by the resilient mount 38 in a manner to bedescribed. The lower spring plate 42 may be either concentric ornon-concentric with respect to the shock absorber casing 32, dependingupon the particular model vehicle involved.

Referring now to FIG. 2, the upper spring plate 44 has a rubber bushing46 which is secured beneath its central portion by integral tabs 48 andsuitable fasteners 50 such as the nuts and bolts illustrated in FIG. 2.The piston rod 36 slides freely in the rubber bushing 46 so that thebushing 46 serves as a resilient stop or bumper for the end of the shockabsorber casing 32. The fasteners 50 also secure a cylindrical dustshield 52 to the upper spring plate 44 for protecting the upper end ofthe casing 32 and the piston rod 36.

The resilient mount 38 comprises an annular stamped metal mounting plate52, an elastomeric ring 54, a central metal sleeve 56 having an attachedend plate 58, and a ball thrust bearing which includes an upper racering 60, a lower race ring 62 and a full complement of bearing balls 64.

The mounting plate 52 has a flat outer flange 66 which is used to securethe resilient mount 38 to the vehicle body structure 12 and a cup-shapedcentral portion 68. The cup-shaped portion 68 is connected to the flatouter flange 66 by an asymmetrical transition 70 which changes from adepressed U-shaped section to a projecting L-shaped section and backagain in the circumferential direction. The transition 70 accommodatesthe orientation of the flat outer flange 66, the sleeve axis 56a and thebearing axis 60a required for a particular vehicle and may not benecessary for other vehicle designs.

The cut-shaped portion 68 is embedded in the elastomeric ring 54 and hasa pierced bottom wall which provides a radial lip 72 which surrounds thesleeve 56 in a spaced concentric relationship. The radial lip 72 isdisposed between a cup-shaped head 74 of the sleeve 56 and an end plate58 attached to the lower end of the sleeve. The radial lip 72 projectsradially inwardly of the head 74 and end plate 58 to provide a fail-safedevice for retaining the piston rod 36 in the event the inner portion ofthe elastomeric ring 54 shears.

The mounting plate 52, elastomeric ring 54, central sleeve 56 and upperrace ring 60 are formed as a subassembly in which the elastomeric ring54 is bonded to the mounting plate 52, the central sleeve 56 and theupper race ring 60 as shown in FIG. 3. This subassembly may be formed bymolding and vulcanizing the elastomeric ring 54 in a suitable mold whichproperly positions the mounting plate 52, central sleeve 56 and upperrace ring 60 in the mold cavity.

The cup-shaped portion 68 has an exposed upper flange 68a which has aplurality of apertures 68b which receive mold pins to produce voids 76and 78 in the outer portion of the elastomeric ring 54. The number anddepth of these voids are selected to provide a predetermined independentresilience or spring rate for the outer portion of the elastomeric ring56 which supports the coil spring 40 via the bearing 60, 62, 64 and theupper spring plate 44. These voids can also be patternedcircumferentially to provide lateral support for the coil spring 40which has one stiffness in the longitudinal direction of the vehicle andanother stiffness in the side direction.

The elastomeric ring 54 is molded around the outer edge of the upperrace ring 60 and has integral flexible inner and outer circumferentiallips 80 and 82 at the lower end of the elastomeric ring 54 concentricwith the mold bonded upper race ring 60.

The central portion of the elastomeric ring 54 has a shallow cavity atits lower end which provides a scalloped ledge 83 inside the innerflexible lip 80 for lightly supporting the end plate 58 after it isassembled as shown in FIG. 2. During suspension jounce and rebound theforces of the piston rod 36 are essentially resisted entirely by theportion of the elastomeric ring 56 inside the cup-shaped portion 68 evenwhen the piston rod 36 moves upwardly with respect to the resilientmount 38. Consequently the resilience or spring rate for the portion ofthe elastomeric ring 54 which supports the shock absorber 30 isindependently predetermined by the sizes, shapes and relative proximityof the upper end of the sleeve 56 (including its cup-shaped head 74) andthe cup-shaped portion 68 of the mounting plate 52. These parameters areselected to produce the stiffness desired.

The portion of the elastomeric ring 56 inside the cup-shaped portion 68also provides a relatively stiff lateral support for the piston rod 36.The cardanic flexibility of the sleeve 56 and the piston rod 36 can beincreased while still retaining a relatively stiff lateral support byproviding an annular void 54b around the lower portion of the sleeve 56during the molding process.

The resilient mount 38 is produced from the subassembly by adding theend plate 58, the bearing balls 64 and the lower race ring 62. The endplate 58 is mounted on the reduced lower end portion of the centralsleeve 56 which is then spun over to secure the end plate 58 as shown inFIG. 2. The primary function of the end plate 58 is a fail-safe deviceand it does not appreciably affect the resilient support of the pistonrod 36 as noted above.

The ball thrust bearing is completed by inverting the subassembly fromits upright postion shown in FIG. 3 and supporting the complement ofbearing balls 64 on the upper race ring 60. The lower race ring 62 isthen placed on the bearing balls 64 with its inner and outer edgespartially inserted beneath the lips 80 and 82. The lower race ring 62 isthen rotated into place, similar to a wheel being mounted on a tire, todispose the entire inner and outer edges inside the lips 80 and 82. Thelips 80 and 82 then retain the lower race ring 62 and seal the inner andouter ends of the thrust bearing, respectively.

The resilient mount 38 supports the upper end of the MacPherson strut onthe vehicle body structure 12 as illustrated in FIGS. 1 and 2. Moreparticularly, the flat outer flange 66 of the mounting plate 52 issecured to the vehicle body structure 12 by suitable fasteners 84, suchas the nuts and bolts shown in FIG. 2. The piston rod 36 of the shockabsorber 30 is attached to the resilient mount 38 by a reduced upper endwhich is held in the central sleeve 56 by a bolt threaded onto the endof the piston rod. The upper spring plate 44 has an inner conic lip 86which is biased against a similarly shaped portion of the lower racering 62 by the coil spring 40.

The resilient mount 38 provides the following advantages. The moldbonding of the mounting plate 52 and the upper race ring 60 to theelastomeric ring 54 permits the replacement of the two retainers of theprior art with a single mounting plate which eliminates a part and savesweight while at the same time improves the alignment and contactinterface of the bearing 60, 62, 64 with the elastomeric ring 54. Theintegral flexible retaining and sealing lips 80 and 82 of theelastomeric ring 54 reduces the complexity of the ball thrust bearing ofthe prior art which required a second molding operation to provide seallips on the lower race ring and preassembly of the bearing. The innercup-shaped portion 68 of the mounting plate 52 which is embedded in theelastomeric ring 54 more clearly defines the respective spring portionssupporting the coil spring and the piston rods. These portions areeasily independently designed to provide the desired stiffnesscharacteristic for the coil spring 40 and the shock absorber 30 by theuse of voids in the elastomeric ring 54 on the one hand and the shape,size and relative proximity of the central cup portion 68 and sleeve 56on the other hand.

In the above embodiment of the invention, the motions of the piston rod36 during suspension jounce and rebound are opposed primarily by theshear resistance of the central portion of the elastomeric ring 54because the central sleeve 56 is bonded to the elastomeric ring 54. FIG.5 discloses an alternate embodiment wherein the motions are opposedprimarily by the compressive resistance of the central portion.

The resilient mount 138 is substantially the same as the resilient mount38 except for the following modification. The central sleeve 156 of theresilient mount 138 is not bonded to the elastomeric ring 154 and isattached after the annular mounting plate 152 and upper bearing ring 160have been mold bonded to the elastomeric ring 154 to form a subassembly.The cup-shaped portion 168 of the mounting plate 152 which is embeddedin the elastomeric ring 154 is closer in shape and proximity to theenlarged cup-shaped head 174 of the sleeve 156. The central portion ofthe elastomeric ring 154 below the radial lip 172 more actively resistsmovement of the piston rod by virtue of the annular bumper 183 oftriangular cross section which engages the end plate 158 attached to theend of the central sleeve 156. The end plate 158 is also preferablyattached to the central sleeve 156 so that the central portion of theelastomeric ring 154 is compressively preloaded to a sufficient degreeso that the central portion is always subjected to compressive forces bythe piston rod movements. Downward movement of the piston rod isresisted primarily by the compression resistance of the elastomeric ringportion inside of the cup-shaped portion 168. Consequently stiffness inthe downward direction is predetermined by the relative sizes, shapesand proximities of the enlarged head 174, the upper end of the sleeve156 and the cup-shaped portion 168 as before. Upward movement of thepiston rod on the other hand is resisted primarily by the compressionresistance of the portion between the radial lip 172 in general and theannular bumper 183 in particular which is shaped to provide apredetermined stiffness. The modified design has all of the advantagesof the first embodiment with the additional advantage that differentstiffness characteristics can be provided for the upward and downwardmovements of the piston rod.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described, for obviousmodifications will occur to a person skilled in the art.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A resilient mount forthe upper end of a vehicle suspension strut comprising a shock absorberhaving an outer casing and a piston rod extending out of its upper end,and a coil spring surrounding the shock absorber and supported at itslower end by a spring plate attached to the outer casing, comprising:anannular mounting plate for securing the resilient mount to vehiclesupport structure bonded to an upper surface of an elastomeric ring forcushioning the loads of the coil spring as well as the loads of theshock absorber during suspension jounce and rebound, an upper race ringbonded to a lower surface of the elastomeric ring and spaced from acup-shaped central portion of the annular mounting plate embedded in theelastomeric ring, thrust bearing means for rotatably supporting theupper end of the coil spring comprising the upper race ring bonded tothe elastomeric ring, and a complement of bearing elements and a lowerrace ring retained in assembly with the elastomeric ring by integralflexible lips at the lower end of the elastomeric ring which engage thelower race ring to seal the inner and outer ends of the thrust bearingmeans, and a central sleeve secured to the elastomeric ring forattaching the end of the piston rod of the shock absorber having anenlarged head disposed inside of the cup-shaped central portion of theannular mounting plate with a portion of the elastomeric ring disposedtherebetween.
 2. A resilient mount for the upper end of a vehiclesuspension strut comprising a shock absorber having an outer casing anda piston rod extending out of its upper end, and a coil springsurrounding the shock absorber and supported at its lower end by aspring plate attached to the outer casing, comprising:an annularmounting plate for securing the resilient mount to vehicle supportstructure bonded to an upper surface of an elastomeric ring forcushioning the loads of the coil spring as well as the loads of theshock absorber during the suspension jounce and rebound, an upper racering bonded to a lower surface of the elastomeric ring and spaced fromthe annular mounting plate, said annular mounting plate having acup-shaped central portion which is embedded in the elastomeric ring andhas an outer diameter less than the inner diameter of the upper racering, thrust bearing means for rotatably supporting the upper end of thecoil spring comprising the upper race ring bonded to the elastomericring, and a complement of bearing elements and a lower race ringretained in assembly with the elastomeric ring by integral flexible lipsat the lower end of the elastomeric ring which engage the lower racering to seal the inner and outer ends of the thrust bearing means, and acentral sleeve secured to the elastomeric ring for attaching the end ofthe piston rod of the shock absorber disposed inside of the cup-shapedcentral portion of the annular mounting plate with a portion of theelastomeric ring disposed therebetween, and an end plate which isattached to the central sleeve and abuts a lower surface of theelastomeric ring radially inward of the flexible lips, the cup-shapedcentral portion having a radial lip which is embedded in the elastomericring between the enlarged head of the central sleeve and the end plateattached to it and defines a hole smaller than the head and the endplate.
 3. The resilient mount as defined in claim 2 wherein the centralsleeve is mold bonded to the elastomeric ring so that axial movement ofthe central sleeve relative to the annular mounting plate is opposedprimarily by the shear resistance of the elastomeric ring portion insideof the cup-shaped portion of the mounting plate.
 4. The resilient mountas defined in claim 2 wherein the central portion of the elastomericring is compressively preloaded by the central sleeve and end plate andthe axial movement of the central sleeve relative to the mounting plateis opposed primarily by the compressive resistance of the centralportion of the elastomeric ring. .Iadd.
 5. A resilient mount for theupper end of a vehicle suspension strut comprising a shock absorberhaving an outer casing and a piston rod extending out of its upper end,and a coil spring surrounding the shock absorber and supported at itslower end by a spring plate attached to the outer casing, comprising:anannular mounting plate for securing the resilient mount to vehiclesupport structure bonded to an upper surface of an elastomeric ring forcushioning the loads of the coil spring as well as the loads of theshock absorber during suspension jounce and rebound, an upper race ringbonded to a lower surface of the elastomeric ring and spaced from acup-shaped central portion of the annular mounting plate embedded in theelastomeric ring, thrust bearing means for rotatably supporting theupper end of the coil spring comprising the upper race ring bonded tothe elastomeric ring, a complement of bearing elements and a lower racering, said elastomeric ring having integral flexible lips at the lowerend which engage the lower race ring so that the inner and outer ends ofthe thrust bearing means are sealed and at least one said lip retainsthe lower race ring in assembly with the elastomeric ring, and a centralsleeve secured to the elastomeric ring for attaching the end of thepiston rod of the shock absorber having an enlarged head disposed insideof the cup-shaped central portion of the annular mounting plate with aportion of the elastomeric ring disposed therebetween. .Iaddend. .Iadd.6. The resilient mount as defined in claim 5 wherein the integralflexible lips at the lower end of the elastomeric ring comprise innerand outer circumferential lips for sealing the inner and outer ends ofthe thrust bearing means respectively. .Iaddend. .Iadd.7. The resilientmount as defined in claim 6 wherein the lower race ring is retained inassembly with the elastomeric ring by an inner edge of the lower racering being disposed inside the outer circumferential lip. .Iaddend..Iadd.8. The resilient mount as defined in claim 6 wherein the lowerrace ring is retained in assembly with the elastomeric ring by an outeredge of the lower race ring being disposed inside the outercircumferential lip. .Iaddend. .Iadd.9. The resilient mount as definedin claim 6 wherein the lower race ring is retained in assembly with theelastomeric ring by inner and outer edges of the lower race ring beingdisposed inside the inner and outer circumferential lips respectively..Iaddend. .Iadd.10. A resilient mount for the upper end of a vehiclesuspension strut comprising a shock absorber having an outer casing anda piston rod extending out of its upper end, and a coil springsurrounding the shock absorber and supported at its lower end by aspring plate attached to the outer casing, comprising:an annularmounting plate for securing the resilient mount to vehicle supportstructure bonded to an upper surface of an elastomeric ring forcushioning the loads of the coil spring as well as the loads of theshock absorber during suspension jounce and rebound, an upper race ringbonded to a lower surface of the elastomeric ring and spaced from theannular mounting plate, said annular mounting plate having a cup-shapedcentral portion which is embedded in the elastomeric ring and has anouter diameter less than the inner diameter of the upper race ring,thrust bearing means for rotatably supporting the upper end of the coilspring comprising the upper race ring bonded to the elastomeric ring, acomplement of bearing elements and a lower race ring, said elastomericring having integral flexible lips at the lower end which engage thelower race ring so that said lips seal the inner and outer ends of thethrust bearing means and at least one said lip retains the lower racering in assembly with the elastomeric ring, a central sleeve secured tothe elastomeric ring for attaching the end of the piston rod of theshock absorber disposed inside of the cup-shaped central portion of theannular mounting plate with a portion of the elastomeric ring disposedtherebetween, and an end plate which is attached to the central sleeveand abuts a lower surface of the elastomeric ring radially inward of theflexible lips, the cup-shaped central portion having a radial lip whichis embedded in the elastomeric ring between the enlarged head of thecentral sleeve and the end plate attached to it and defines a holesmaller than the head and the end plate. .Iaddend. .Iadd.11. Theresilient mount as defined in claim 9 wherein the integral flexible lipsat the lower end of the elastomeric ring comprises inner and outercircumferential lips for sealing the inner and outer ends of the thrustbearing means respectively. .Iaddend. .Iadd. . The resilient mount asdefined in claim 11 wherein the lower race ring is retained in assemblywith the elastomeric ring by an inner edge of the lower race ring beingdisposed inside the inner circumferential lip. .Iaddend. .Iadd.13. Theresilient mount as defined in claim 11 wherein the lower race ring isretained in assembly with the elastomeric ring by an outer edge of thelower race ring being disposed inside the outer circumferential lip..Iaddend. .Iadd.14. The resilient mount as defined in claim 11 whereinthe lower race ring is retained in assembly with the elastomeric ring byinner and outer edges of the lower race ring being disposed inside theinner and outer circumferential lips respectively. .Iaddend.